Chapter 12: Air Masses and Fronts I) Air mass: large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given latitude A) Source regions: regions where air masses originate 1) Good source region is generally flat with uniform composition and light surface winds 2) Longer air remains stagnant over source region or longer the path over which the air moves the more likely it will acquire properties of the below surface 3) Ideal regions are dominated by surface high pressure a) Ice and snow covered artic plains in winter b) Subtropical oceans in summer B) Middle latitudes is transition zone where air masses with different physical properties move in, clash, and produce weather activity C) Classified according to their temperature and humidity 1) Grouped into four general categories according to their source region

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